Process for the concentration of boron chemically combined from its ores by autoflotation



Aprll 27, 1943. F sg- E 2,317,413

PROCESS FOR THE CONCENTRATION OF BORON CHEMICALLY COMBINED FROM ITS ORES BY AUTO-FLOTATION Filed Sept. 11, 1940 "F/G. ORE

v GRIND THRU es MESH TREATMENT SOLUTION TANK T of and OTHER SALTS CE] DEPRESSANTS ROUGHER T and/O, ROTATION Ti-ULS |-|F|| TERHso| u low}- METALLIC SALTS CELLS i o i g Isouosf {El 1 CONCENTRATE g x v I I E E l g L CLEANER CELLS i g I T i E LEACHING TANK CONCENTRATE I mmouwss IFILTER (OENTRIFUGE) J souo H3503 [El CON T SATURATED H; BO;

1 SOLUTION RECRYSTALLIZATION FILTER ENT EI CELLS I i1 PURIFIED q MAR|'(ET 3 3 SOLUTION T/NVENTOR Patented Apr. 27, 1943 UNITED, STATES PATENT 'OFFI-C'E PROCESS FOR THE CONCENTRATION OF BORON CHEMICALLY COIWBINED FROM ITS ORES BY AUTOFLOTATION Francis Keith Shelton, Boulder City, Nev., as-

signor to the Government of the United States, as represented by the Secretary of the Interior, and his successor or designee Application September 11, 1940, Serial No. 356,300

4 Claims.

(Granted under .the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) The invention described herein may be manufactured and used by or for the Govermnent of i collecting material, but I in no way limit myself by this explanation. When chemically combined boron in ores is treated with acidic materials, I

have further found that the resulting boron compounds are readily concentrated by a froth flotation operation, in the absence of organic frothing and/or collecting reagents, i. e. by auto-flotation. The grade of the boron compound concentrates is generally raised by the use of organic depressing reagents, and/or some metallic salts. The matty froth frequently produced is usually advantageously effected by certain metallic salts, optionally in the presence of organic depressing reagents. Provision is made for the optional step of recrystallization of the flotation concentrates to provide a high-grade boric acid product.

The boron compounds of the ores may be either solids or solutes. The word ore is herein used to include both categories. Saline solutions of boron compounds are readily concentrated by this process. I use th term boric acid to designate either sassalite or, more commonly, the boron compounds resulting from the treatment of the ores of boron by acidic materials.

I have experimentally reacted the ores with concentrated and dilute acids, and with gases forming acid solutions with water. By reacting the materials in other methods which will result in boric acid being formed in the solution of the flotation cell, similar results should be obtained. Boric oxide, for example, in contact with water will give boric acid, and hence could be concentrated by the present method. The process herein described is not dependent upon the method of formation of the boric acid. I make no claim to invention of' methods of reacting materials to form boric acid.-

Aoids and acid-forming compounds which in water solutions will give a pH of less than about 5.0, will react with the commercial boron minerals (colemanite, ulexite, kernite and borax) to give solid boric acid, and the term acidic material as used in the appended claims, designates -ma-- terials which in water solution will give a pH of .less than 5.0:, It is known (U. s. Patent 1,108,-

129) that carbon dioxide, under pressure, will release boric acid from.. alkaline earth borates. Any acid which, in the absence of deleterious other reactions, will release free solid boric acid will produce the desired result. Sulphuric and sulphur dioxide have proven experimentally good. Chemically there are a large number of equivalents of these, some of 'which we have tested, forexample, muriatic and nitric acids. The choice of acidic material-that is, acidsor acid forming compounds-will doubtless be for economic reasons rather than for chemical ones.

The froth from the auto-flotation of boric acid, particularlythat acid formed within the ores by acid reactants, has a texture which sometimes floats undesirable amounts of the gangue materials, e. g., clays and the salts found in flotation pulp. I have found that some metallic salts, such as copper sulphate and aluminum sulphate, act to modify the froth texture, which modification generally aids in raising the grade of the concentrates; These froth controlling metal salts are ones whose cations form insoluble borates. Such salts can virtually destroy the boric acid froth when more than about 1 /2 to 5 lbs/T of ore are added to the flotation pulp. In such concentrations, pine oil or other recognized frothers may be used to concentrate the acid. The froth modification is usually aided by organic compounds,

such as starch, corn dextrine, quebracho, gum

vent the flotation of the gangue materials, and

particularly of the clay (see Wenig, Trend of Flotation, Colorado School of Mines Quarterly,

October, 1937, page 20) also may be used to raise the grade of the concentrate in absenc of orgame flotation reagents, as was not predictable prior to my discovery.

The aqueous solution in which the flotation partial. The coating of the reaction product, be

it complete or incomplete, on a solid boron compound, will -sometimes allow the latter to be floated into the flotation concentrate.

When I use gaseous reactant materials, such as sulphur dioxide, or when gases are released-from the ores by the treatment thereof by acidic materials, I include as flotation the phenomena ob served, to-wit: the excess and/or released gas will sometimes float the resultant boron compounds as a froth. The result by separating this froth is comparable to the more formal method of flotation.

I have further found that th flotation concentrate obtained in the herein described manner may be purified as anoptional step in the process by recrystallization methods heretoforepracticed. This recrystallization of the boric acid is not claimed as invention apart from its combination as a step of a new process including the froth flotation of boric acid without reagents, herein termed the auto-flotation of boric acid.

The flow diagram, Fig. 1, for the concentration of colemanite ores expresses my invention of a process for the manufacture of substantially pure boric acid. One skilled in the art of flotation will recognize variations therefrom, and steps therein which constitute invention. In this flow diagram dotted flow lines are used to indicate optional procedures.

I shall now describe the mannerin which the novel process has been used in actual separation of boron chemically combined from its ores.

- EXAMPLE 1 250 grams of 14 mesh commercial boric acid, analyzing 54.7 percent B20: was ground in saturated solution of the boric acid in a pebble mill for 30 minutes. The resulting pulp was placed in a 500 gram sub-A (Fahrenwald) laboratory flotation machine, diluted to 2500 ml. of the saturated solution and a flotation test completed without the'addition of reagents. 99.5 percent 'of the solid acid was floated as a concentrate.

which concentrate had a grade of 56.1 percent B203.

- EXAMPLE 2 400 grams of a 35 mesh partially concentrated colemanite ore, containing some ulexite, analyzing 35.5 percent B203 was mixed with- 130.8 ml. of 1.83 sp. gr. sulphuric acid and 1000 m1. of a solution saturated with the reaction products in a previous similar test; and the mixture allowed to react for 47 hours. The pulp was EXAMPLE 3 400 grams of 20 mesh colemanite ore analyzing 15.67 percent 1320; was pulped with 1000 ml. or a similar solution to that used in Example 2. 115 ml. of concentrate sulphuric acid was added, the mixture heated 1% hours and further 5 reacted for 22 /2 hours. The pulp was then placed in a flotation cell, 1500 m1. of the solution added and a flotation operation completed without organic reagents. 87.1 percent of the boron present in the'products was held in the concentrate which had a grade of 45.46 percent v ExAuPLs 4 400 grams of a -65 mesh partially concentrated colemanite ore analyzing 31.00 percent B: was pulped with 1000 ml. of a solution containing 43.3 grams per liter of boric acid, and sulphur dioxide gas bubbled through this pulp for 1 hour. The reacted pulp was placed in a flotation cell, 1500 ml. of a boric acid solution containing 44.3 grams per liter of boric acid added, and a flotation operation completed, without reagents. 99.0 percent of the boron present in the flotation products was recovered in the concentrate, which concentrate had a grade of 41.56 percent B203.

EXAMPLE 5 To determine the advantages obtainable through the use of the organic depressing reagents alone or in combination with the metallic salts, a series of tests were made. .The combination ctmetallic salts and organic depressing re- ..agents upon the froth was also proven-helpful in these tests. Test conditions were: 400 grams of raw colemanite ore (tests 132 to 144, this ore analyzed 15.67 percent B203; tests 148 to 167. 19.53 percent Boos) was ground through 65 mesh, pulped with 1,000 ml. of a solution practically saturated with the reaction products, sul-. phur dioxide bubbled through the pulp for 2 hours, the reacted pulp placed in a flotation cell, diluted to about 2500 ml. with more of the solution, the indicated reagents added, and a flotation operation completed. The test from Example 4 is included in this table for comparison.

Table 1 Pertcen Test Depressant Point added Quantity B10;

concentrate 41.56 Rougher. 1% 48.38 1st ceaner- 45.46

0..... 2nd clean RougheL 1% 48.37 148. do lstceane 46.29 152. Gum arabic Rcugher.-- 1% 40.48 153... Quebracho ext- 1% 51.36 156.-- do 1st cleaner M 51.71 162.-- Corn dextrine. d 1% 47.56 163.-. NalSiO; Rougher- 1% 47.06 {ne r} M Qimbrdfi' do::: 1% {gms oc w gt en ine:

no me oex oug er {OuSO4 1st cleaner EXAMPLE 6 A salt mass from Searles Lake containing alkali metal borates, analyzing 11.2 percent B203,

in association with other alkali metal salts was treated in a solution saturated with both the salt mass and boric acid, with sulphur dioxide for hour. The reacted pulp was treated by a flotation apiiiatign. The results are summarized in A raw colemanite ore, analyzing 19.53 percent B203, was treated with sulphur dioxide'as in Example 5, and a flotation operation performed using 0.2 lb./T of copper sulphate to modify the froth characteristics and a flotation operation completed without organic reagents. A concentrate analyzing 47.32 percent B20: was obtained, which held 86.4 percent of the boron present in the ore. Aluminum sulphate proved experimentally equivalent to the copper sulphate.

EXAMPLE 8 A solution of the Searles Lake salt mass of Example 6 containing 44.8 grams per liter of B20: was treated with sulphur dioxide for 2 hours hour or less subsequently proved eificient), and the resultant mixture subjected to a froth flotation operation. A concentrate analyzing 55.14 percent B20: was obtained.

. EXAMPLE 9 Treating the boric acid flotation concentrates from a colemanite ore in suflicient heated water (saturated with boric acid at the normal temperature) to dissolve the'boric acid, separating the undissolved material, and thereafter cooling the solution, high-grade boric acid was precipitated. Two examples are given in "able 3.

Table 3 Test No. i No. 2

Grade 11:30; in flotation concentrates 83. 74 84. 88 Grade HQBOI in recrystallized concentrates--. 99. 9 100. Percentage of total HzBOl in recrystallized 0. rates 99. 44 98 EXAMPLE 10 400 grams of raw colemanite ore, analyzing 15.67 percent B20: was ground through mesh pulped with 1000 ml. of solution similar to that obtainable from the flotation' products of Example 4, sulphur dioxide bubbled through the mixture for 4 hours (2 hours or less was subsequently proved as .eflicient), the reacted pulp placed in a flotation cell, 1300 ml. of the same solution added, and a flotation test completed. 93.3 percent of the boron present in the products was held in the concentrate; this concentrate had a grade of 47.18 B203.

I disclaim invention of processes for the flotation of boric acid with the use of recognized organic frothing reagents, such as pine oil and cresylic acid; within the scope of this invention, they are superfluous reagents. of Mines R. I. 3488, pp. 10-11 describes the flotation of boric acid with the use of frothers. The U. S. Bureau of Mines R. I. 3525, June 1940 is a report upon the present'invention.

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In the auto-flotation of boric acid, the step which comprises floating the boric acid in the presence of froth-controlling metallic salts whose cations form insoluble borates, said salts being selected from the group consisting of aluminum and copper salts.

2. In the auto-flotation of boric acid, the step which comprises floating boric acid in the presence of protective colloid depressing agents and metallic salts whose cations form insoluble borates, said salts being selected from the group consisting of aluminum and copper salts.

3. In the auto-flotation of boric acid, the step which comprises floating the acid in the presence of protective colloid depressing agents.

4. In the auto-flotation of boric acid, the step which comprises floating the acid in the presence of sodium silicate, a metallic salt depressing agent which through dispersion of the ore pulp tends to prevent flotation of the gangue materials and particularly of the clay.

F. KEITH SHELTON.

The U. S. Bureau,

CERTIFICATE OF CORRECTION:

Patent No. 2,317,l 15'., April 27, 1915.

FRANCIS KEITH SHELTON.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, sec-- 0nd column, line 19, for "R. I. 511.88" read. --R. I. 5158"; and in the drawing, the signature thereto should appear as shown below instead of as now printed INVENTOR I Ff Aeifb She/fan, ATTOI? E) 4 and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 22nd day of June, A. D. 1915.

Henry Van Arsdale,

(Seal) Acting Commissioner of Patents 

